Bipolar transistors of either the NPN or PNP type require contacts usually through suitable contact holes to the base, collector and emitter regions. Ordinarily these contacts are formed of a conductive metal such as aluminum or a combination of chromium and gold. Examples of bipolar transistors having metal base, collector and emitter contacts are shown in U.S. Pat. No. 3,855,007 issued Dec. 17, 1974 to Polata et al, U.S. Pat. No. 3,885,494 issued May 27, 1975 to Millar, U.S. Pat. No. 3,943,555issued Mar. 9, 1976 to Mueller et al and U.S. Pat. No. 3,971,059 issued July 20, 1976 to Dunkley et al.
It is also known that polysilicon material may be used to form the gate of a bipolar device. In U.S. Pat. No. 4,050,965 issued Sept. 27, 1977 to Ipri et al, a method for fabricating a bipolar transistors is described which includes a gate formed of polysilicon material and wherein the edge of the polysilicon gates serves as the diffusion edge for both the base and emitter difusions. In this patent however, metal interconnects are used for the base, emitter and collector and is therefore different from the method and structure of the present invention.